It's possible he was referring to either 3rd Seat, Lieutenant position or Captain position, and as for the Squad, he could mean any squad. if your referring to a bit of his speech with the twins in front of all the captains minus 3,5 and 9 i would assume he meant he would appoint the twin to the Captains Seat of a empty squad meaning they would have the choice of which one they'd want to take charge of but its assumed never fully stated.